The invention is related to the field of safety restraint systems for automotive vehicles and, in particular, to a retractor for the shoulder webbing having a self-zeroing center of gravity assembly.
Currently with the advent of reclining seats in automotive vehicles and the shoulder webbing of the safety restraint system still being pivotably attached to the pillar or other stationary structural member of the vehicle, the shoulder webbing of the safety restraint system is not fitted properly to the occupant when the seat is reclined. One solution to this problem is to mount the retractor for the shoulder webbing of the safety restraint system directly on the seat. However, problems are encountered as the backof the seat is displaced from an upright position to a reclined position. First, the shoulder webbing is extracted as the seat is reclined which may cause the retractor to lock up and prohibit the reclining of the seat. Further, the acceleration sensor is now at an angle to the vertical axis of the vehicle resulting in a decrease in is sensitivity.
The object of the invention is a retractor for the shoulder webbing of a safety restraint system mountable to the back of the seat in which the center of gravity assembly incorporating an acceleration (vehicle) sensor is self-zeroing independent of the position of the back of the seat between an upright and reclined position.
Another object of the present invention is to pivotably attach the retractor to a structural member of the back of the seat so that the shoulder webbing will properly fit the occupant independent of the position of the back.
Still another object of the present invention is to provide a mechanism responsive to at least a predetermined length of the shoulder webbing being wound on the spool of the retractor to inhibit the lock-up of the spool.
Yet another object of the present invention is a blocking mechanism responsive to the extraction of shoulder webbing from the retractor's spool to temporarily block the pivoting of the center of gravity assembly in response to the unwinding of the shoulder webbing from the spool.
Accordingly the invention comprises a retractor having a frame mounted to a structural member of the back of the seat and a spool rotatably mounted to the frame having one end of the shoulder belt webbing attached thereto. The retractor includes means attached to one end of the spool for producing a rotary torque tending to wind the shoulder belt webbing on the spool and a ratchet wheel attached to the opposite end.
A center of gravity assembly is attached to the frame and is pivotable about an axis substantially normal to the rotation axis of the spool. The center of gravity assembly has its center of gravity located below the pivot axis such that it remains aligned with the gravitational field independent of the position of the seat back. The center of gravity assembly includes an acceleration sensor producing a mechanical output in response to acceleration greater than a predetermined value.
A lock pawl is pivotably attached to the frame and is displaceable between a disengaged and an engaged position with the ratchet wheel. In the engaged position, the lock pawl prohibits the rotation of the ratchet wheel and of the spool in a direction to unwind the shoulder belt webbing therefrom. A mechanical link responsive to the mechanical output of the acceleration sensor displaces the lock pawl to the engaged position locking the ratchet wheel and the spool in their current position.
In a preferred embodiment of the invention, the retractor is pivotably mounted to the structural member to pivot about an axis transverse to the longitudinal axis of the vehicle so that the shoulder belt webbing will properly fit about the occupant, has a mechanism responsive to the length of the webbing wound on the spool to prevent the lock pawl from engaging the ratchet wheel when a predetermined length of the shoulder webbing is wound on the spool and a blocking mechanism responsive to the unwinding of the shoulder webbing from the spool to temporarily block the pivoting of the center of gravity assembly.
These and other objects of the invention will become more apparent from a reading of the best mode in conjunction with the drawings.